Acoustic Wave Filter Circuit for Higher-Order Mode Attenuation
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Solution Overview
Problem
Conventional filter devices in communications devices face challenges in achieving improved attenuation and isolation characteristics, particularly in miniaturized designs, due to higher-order mode issues in frequency bands used for carrier aggregation, which affect signal separation and interference suppression.
Innovation Solution
The filter device incorporates a circuit with multiple interdigital transducer (IDT) electrodes and capacitors connected to various terminals and nodes within the filter device, forming a longitudinal-coupling-type acoustic wave resonator or acoustic wave delay line, allowing for flexible phase manipulation and improved attenuation and isolation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional filter device uses TC-SAW elements for miniaturization, then device size is reduced, but higher-order modes occur in frequency bands used for carrier aggregation, degrading attenuation characteristics
Solution Approach 1:
The filter device is divided into multiple filters (first filter, second filter, etc.) each handling different frequency bands. The additional circuit is further segmented into multiple IDT electrodes (at least three) connected to different nodes within the filter device, allowing independent control of attenuation at different frequencies and locations.
Solution Approach 2:
An additional circuit acting as an intermediary element is introduced between the existing filters and ground/reference potential. This circuit includes at least three IDT electrodes connected to different nodes (common terminal, first terminal, second terminal, or intermediate nodes), providing intermediate attenuation control to suppress higher-order modes without affecting the main filter functionality.
2Device complexity
If the filter device structure is simplified for miniaturization, then device complexity is reduced, but isolation between different filters deteriorates
Solution Approach 1:
The additional circuit with multiple IDT electrodes serves multiple functions simultaneously: it provides attenuation in frequency bands for carrier aggregation, improves isolation between different filters, and maintains compatibility with the existing filter structure. This multi-functional approach enhances performance without proportionally increasing complexity.
Solution Approach 2:
Different IDT electrodes are connected to different nodes within the filter device (common terminal, first terminal, second terminal, or intermediate nodes), providing locally optimized attenuation characteristics at specific locations where higher-order modes or isolation issues occur, rather than applying a uniform solution throughout the device.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the attenuation and isolation performance of the filter device, effectively suppressing higher-order modes and improving signal separation, thereby supporting better communication efficiency in miniaturized communication devices.
Implementation Method 1
an additional circuit including at least three interdigital transducer (IDT) electrodes each connected to a respective one of a corresponding at least three connection points within the filter device
Implementation Method 2
at least three interdigital transducer (IDT) electrodes each connected to a respective one of a corresponding at least three connection points
Implementation Method 3
The at least three IDT electrodes may preferably constitute a longitudinal-coupling-type acoustic wave resonator or an acoustic wave delay line
Implementation Method 4
The at least three IDT electrodes may preferably constitute a longitudinal-coupling-type acoustic wave resonator or an acoustic wave delay line
Data Source
AI summary
A filter device having improved attenuation and isolation characteristics. In one example the filter device has a common terminal, a first terminal, and a second terminal, and includes a first filter connected between the common terminal and the first terminal, a second filter connected between the common terminal and the second terminal, and an additional circuit including at least three IDT electrodes each connected to a respective one of a corresponding at least three connection points within the filter device, the at least three connection points being selected from a group consisting of the common terminal, the first terminal, the second terminal, a first node disposed between the plurality of first filter elements along a path extending between the common terminal and the first terminal, and a second node disposed between the plurality of second filter elements along a path extending between the common terminal and the second terminal.